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Ergonomists need easy-to-use, quantitative job evaluation methods to determine potential risk factors for cumulative trauma disorders (CTDs) in field-based epidemiology studies. One device that may provide an objective measure of exposure to repetitive work is an activity monitor. The activity monitor detects and records acceleration with a sampling frequency of 10 HZ. A preliminary study included 157 workers in an appliance assembly plant who wore activity monitors on their wrists for a minimum of 50 minutes while performing their jobs. The workers who were monitored. were members of three different groups: (1) 82 workers from a traditional washing machine assembly line, (2) 13 from a new (horizontal axis) washing machine assembly line, and (3) 63 salary workers (clerical, managers). A 50-minute geometric mean was computed for each study participant. When comparing the means by group, there was a statistically significant difference between groups (p=0.0001). This investigation confirmed the expectation that traditional washing machine workers would have much greater arm motion acceleration characteristics than salaried workers. Furthermore, the arm motion acceleration of workers on the new line were lower than for workers on the traditional line, but higher than the salaried workers. The new washing machine line was not in full production and, therefore, repetition rates were not expected to be as high as on the traditional line. A follow-up study was conducted to further discriminate between repetitive assembly jobs. Because the preliminary data showed a strong difference between groups, data collection was limited to the traditional washing machine line; 66 workers wore the monitors for 50 minutes on 4 different days. There was a statistically significant difference between jobs (p=0.0001). Activity monitors were found to be easy-to-use, Nonintrusive devices that can distinguish acceleration rates among assembly jobs.